1. Field of the Invention
The present invention relates to systems and methods for testing wireless devices that requires synchronization of test equipment and wireless device as part of the test sequence.
2. Related Art
Many of today's handheld devices make use of wireless “connections” for telephony, digital data transfer, geographical positioning, and the like. Despite differences in frequency spectra, modulation methods, and spectral power densities, the wireless connectivity standards use synchronized data packets to transmit and receive data.
In general, all of these wireless-connectivity capabilities (e.g., WiFi, WiMAX, Bluetooth, etc.) are defined by industry-approved standards (e.g., IEEE 802.11 and IEEE 802.16) which specify the parameters and limits to which devices having those connectivity capabilities must adhere.
At any point along the device-development continuum, it may be necessary to test and verify that a device is operating within its standards' specifications. Most such devices are transceivers, that is, they transmit and receive wireless RF signals. Specialized systems designed for testing such devices typically contain subsystems designed to receive and analyze device-transmitted signals, and to send signals that subscribe to industry-approved standards so as to determine whether a device is receiving and processing the wireless signals in accordance with its standard.
The testing environment consists of the device, the tester, and a computer controller. The computer and tester work together to capture a device's transmitted signal then analyze it against the specifications provided by the underlying standard; and to send tailored signals to the device to test its receiver capabilities against the specifications of the underlying standard.
A problem that a developer faces in many of today's wireless devices (e.g., cell phones), there is no direct way to control the wireless sub-blocks of the device. In order to control a wireless sub-block one will need to issue a command to the device's CPU which in turn issues a corresponding command to the wireless sub-system. This type of control can increase test time as such communication can be inefficient.
Methods to address this have been proposed (e.g., U.S. Pat. No. 7,689,213, the disclosure of which is incorporated herein by reference). In this type of system the test instrument and wireless system follow a predefined test sequence. For this predefined test sequence to work, the test instrument and wireless system must be synchronized such that the two devices know what the other is to do next.
An issue can arise concerning synchronization in the wireless system which can cause problems for reliable implementation of the above discussed test methodology. This can occur if the software inside the wireless subsystem causes a time delay between issuing a command and when results can be obtained. This delay, in turn, can cause the two systems to go out of sync, as the test equipment is basically sending packets that the wireless sub-system is not observing or receiving. Accordingly, it would be desirable to have a system and method to implement reliable synchronization within systems exhibiting a delay in issuing commands.